1. Field of the Invention
The fundamental field of the invention relates to methods and apparatus used to drill and complete wellbores. Such wellbores include extended reach horizontal wellbores, for example in shales, deep subsea extended reach wellbores, and multilateral wellbores. Relevant to the invention are topics that include liner drilling, deep water drilling, extended reach drilling, Managed Pressure Drilling (MPD), and one of its variants, Constant Bottom Hole Pressure (CBHP) drilling. Specifically, the invention relates to adding simple threaded subassemblies to existing threaded tubular drilling and completion equipment typically already present at a given wellsite that are used to dramatically increase the lateral reach using that existing on-site equipment. These subassemblies extract power from downward flowing clean mud, or other fluids, in an annulus to provide additional force and torque on tubular elements within the wellbore to extend the lateral reach of the drilling equipment and completion equipment. This extra force is provided while maintaining the appropriate circulation. The extra Weight-on-Bit is maintained while continuously maintaining proper circulation. The field of the invention also relates to dramatically reducing the cost to drill new wells by reducing the strength requirements on wellsite drilling and completion equipment to reach a predetermined lateral distance. The field of invention also relates to the reduction in drilling costs of a multiple well drilling program, for example in shales. Such an approach would be particularly useful in the Barnette, Marcellus, and in the Bakken formations.
2. Description of the Related Art
In CSUG/SPE 137821, entitled “New Approach to Improve the Horizontal Drilling reach”, by Vestavik, et al, the Reelwell Drilling Method (RDM) is described. The Dual Drill String (DSS) method is described that uses a Top Drive. The rotating Dual Drill String seals against the interior of a Sliding Piston. The exterior portion of the Sliding Piston seals against the interior of a casing. Applied annular pressure to that Sliding Piston is used to push the Bottom Hole Assembly (BHA) into a horizontal section of a well. Within 10¾ inch casing, Reelwell reports a 14 ton increase in net force applied to the BHA with an applied annular pressure of 50 bar (approximately 725 psi). So, Reelwell does use applied annular pressure to increase Weight on Bit (WOB).
The Reelwell Drilling Method uses the annulus for pressuring their Sliding Piston to increase WOB, and uses the Dual Drill String to maintain circulation while increasing WOB. However, the Dual Drill String is comprised of a pipe-within-a pipe. These concentric pipes are more costly compared to conventional drill pipe, are more complex to assemble in a drilling environment, and require specially trained personnel.
A further significant disadvantage of the RDM, is that the interior of a Dual Drill String is used to circulate fluids both ways. One channel of the pipe system carries clean mud downhole, and the other channel carries dirty mud uphole. Normally, dirty mud goes up an annulus. However, with the DDS, the dirty mud goes up one channel within the DDS, and is therefore called a “reverse circulation” technique (SPE 89505, entitled “Reverse Circulation With Coiled Tubing—Results of 1600+ jobs, by Michel, et. al.”). It is known in the industry that reverse circulation causes an increase in pressure at the bit because the area available to fluid flow up is much smaller compared to the typically available area to annular flow up. Put another way, in reverse circulation, an increase in the pressure on clean mud flowing down the annulus is necessary to compensate for the extra pressure required to push mud up the inside of the drill pipe at the same flow rate. That increase in pressure appears at the drill bit.
This increase in pressure can be defined as a “Back Pressure” and is caused by the frictional fluid flow within pipes and tubulars. Such frictional flow within pipes is well documented in standard text books and can be calculated at the website www.efunda.com. Such increase in Back Pressure can result in drilling conditions outside the desirable pressure range at the intersection of the drill bit with the rock face. That desirable pressure range is called the “Drilling Window” (IADC/SPE 122281, entitled “Managed Pressure Drilling: What It Is and What it is Not”, by Malloy, et. al.).
This increase in Back Pressure can be overcome to some degree by using light oil based drilling mud, but that approach is expensive, and has additional environmental disposal problems. Most importantly, the increase in Back Pressure results in strong limitations on the maximum possible mud flow rate. Reelwell has reported flow rates of less than 200 gallons per minute (SPE 124891, entitled “Reelwell Drilling Method—A Unique Combination of MPD and Liner Drilling”, by Vestavik, et. al.). However, many drilling applications call for about 600 gallons per minute, or more, to carry away rock chips, particularly for long extended reach applications. For a given OD of drill pipe, for example for an OD of 6⅝ inches, Reelwell's Dual Drill String will ALWAYS have a larger Back Pressure when compared to the reverse circulation of just the dirty mud up within a single pipe having the same OD. Such considerations are particularly important for extreme lateral reach drilling with the 5⅞ inch Extreme Reach Drill Pipe available from NOV Grant Prideco (see www.nov.com).
The Reelwell-Telemetry System involving a modification of its Dual Drill String is described in an Award received by Reelwell at the 2010 Offshore Technology Conference (see www.otcnet.org) and it does provide high speed data communications. However, apparently this telemetry system and associated Dual Drill String is not compatible with the standard IntelliServ™ Wired Drill Pipe commercially available today for high speed data communications (see www.nov.com).
For extended reach drilling applications, it may be useful at any given well to use mechanical friction reduction tools and systems. For example, such tools are shown in U.S. Pat. No. 6,585,043 entitled “Friction Reducing Tool” and U.S. Pat. No. 7,025,136 entitled “Torque Reduction Tool”, both assigned to Weatherford. The LoTAD™ (trademark of Weatherford) Mechanical Friction-Reduction System is documented at the website of www.Weatherford.com.
Check valves and pressure relief valves have been used with hydraulic seals to convey coiled tubings into wellbores and for cleaning the wellbores. See U.S. Pat. No. 7,025,142 entitled “Bi-Directional Thruster Pig Apparatus and Method of Utilizing Same”, having the inventor of James Crawford, that describes “changeable, adjustable check valves that are double acting in each direction” to determine the amount of “hydraulic thrust pressure”. OTC 8675 entitled “Extended Reach Pipeline Blockage Remediation”, by Baugh, et. al. describes a sets of relief valves. These all appear to basically spring and ball type check-valve devices. Any such device would be challenged technologically for use in any drilling machine having a clean mud flow rate of 600 gallons per minute, a pressure drop across the device of 725 psi, which therefore, internally dissipates about 250 horsepower within the device. Such technological challenges include at least the following: the heating of such devices dissipating high horsepower would present many problems; the mud at such high flow rates is very abrasive, and the springs, balls, and ball seats, are subject to wear from such high mud flow rates; the mechanisms can clog up or jam; such devices can set up pressure oscillations because of the natural frequencies of the springs and balls and their interaction with tubular structures in the wellbore; the force characteristics of the springs are temperature dependent; the check valves are difficult to maintain in calibration with wear; and such check valves can have relatively complex pressure vs. flow rate characteristics.
Please refer to the section of the specification below under the heading of “References” for precise definitions of the above references cited.